Rain Gauge Fractions: Adding and Subtracting Rainfall

Find a common denominator to add and subtract rain amounts.

Daily rain: fractions

Rewrite the fractions with a common denominator. Then add or subtract.

On Monday the rain gauge showed 1/2 inch. On Tuesday it showed 1/3 inch. How much rain fell on both days?

1/2 + 1/3 = /6 + /6 = /6 inch

Which pair rewrites 3/4 and 5/6 with a common denominator of 12?

A. 3/12 and 5/12B. 9/12 and 5/12C. 9/12 and 10/12D. 6/8 and 5/8

On Wednesday, 2/5 inch of rain fell. On Thursday, 1/4 inch fell. How much rain fell on the two days?

2/5 + 1/4 = inch

The gauge held 7/8 inch of water. On a hot, sunny day, 1/2 inch dried up. How much water is left in the gauge?

7/8 − 1/2 = inch

On Friday, 5/6 inch of rain fell. On Saturday, 1/4 inch fell. How much more rain fell on Friday than on Saturday?

5/6 − 1/4 = inch

Add or subtract the mixed numbers. Regroup when you need to.

In the first week of April, 2 1/3 inches of rain fell. In the second week, 1 1/2 inches fell. How much rain fell in the two weeks?

2 1/3 + 1 1/2 = inches

The town got 4 1/4 inches of rain in spring and 2 2/3 inches in summer. How much more rain fell in spring?

4 1/4 − 2 2/3 = inches

To find 3 1/5 − 1 1/2, Priya rewrites it as 3 2/10 − 1 5/10. What should she do next?

A. Subtract 5 − 2 to get 3/10.B. Add the numerators to get 7/10.C. Rename 3 2/10 as 2 12/10.D. Change both denominators to 20.

Finish Priya's problem.

3 1/5 − 1 1/2 =

10.

Match each problem to its answer.

Sort the totals. Then explain a mistake.

11.

Each card shows the rain from two days. Find each total and sort it.

12.

Ben says 1/2 + 1/4 = 2/6 because 1 + 1 = 2 and 2 + 4 = 6. Explain his mistake and find the correct total.